The present description relates, in general, to methods and controls for internal combustion engines and, more particularly, to methods for controlling diesel engines.
Modern diesel engines uses variable geometry turbines (VGT) to increase the amount of air supplied to the engine cylinders. The VGT varies the angle of the turbine stator inlet vanes to change the amount of air supplied to the engine cylinders.
In addition to providing optimum performance and fuel economy, modern diesel engines must also meet stringent federal regulations on emissions, particularly, particulate matter and nitrogen oxides. In order to meet all of these requirements, diesel engines with a VGT also use an exhaust gas recirculation (EGR) valve that has a variable controlled position to recirculate varying amounts of engine exhaust gases back into the engine cylinders for more complete combustion and reduced engine emissions.
As the engine operates over a large range of operating conditions, including engine speed, fuel usage, engine load, etc., one and typically multiple controllers are embedded in the engine control unit (ECU) to control various engine actuators in response to sensors detecting engine performance in order to optimize engine performance, emissions, etc.
The use of Model Predictive Control (MPC) is growing for engine control. A standard MPC approach incorporates integral type action to guarantee zero state-to-state error that adds additional integral states to the predictive control model. The MPC model uses a number of different engine operating ranges (fuel rate and engine speed), and develops a controller for each range to control the engine actuators.
In a specific example of model predictive control applied to diesel engine airflow, the flows in the engine are controlled using the variable geometry turbine (VGT), EGR throttle, and an EGR valve actuator. These systems are strongly coupled and are highly non-linear.
However, prior applications of model predictive controllers to internal combustion engines and, in particular, to diesel engines have utilized multiple operating ranges of engine performance, each of which has required a separate predictive controller. Further, each predictive controller uses integral type action that presents problems with integrator wind-up.
It would be desirable to provide model predictive controller for use with an internal combustion engine, which has a single step prediction and control horizon for reduced computation time, and memory storage requirements, while at the same time providing zero state-to-state tracking error of engine controlled performance variables.